KR101400406B1 - Method of cnt composite - Google Patents

Abstract

The present invention relates to a method of manufacturing a carbon nanotube composite comprising: a step (step a) of manufacturing a suspension in which carbon nanotubes are dispersed by mixing the carbon nanotubes and solvents; a step (step b) of maintaining the suspension; a step (step c) of manufacturing wet carbon nanotubes by separating the solvents from the suspension; and a step (step d) of manufacturing a carbon nanotube composite by mixing the wet carbon nanotube and a polymer melt. The present invention uniformly improves the electrical properties of carbon nanotubes by dispersing the carbon nanotubes in hydrophilic fluids and hydrophobic fluids through a simple preservation process without a chemical modifier.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing a carbon nanotube composite,

The present invention relates to a method for producing a carbon nanotube composite having improved dispersibility.

Since its discovery in 1991, carbon nanotubes have exhibited superior properties in a variety of applications due to their physicochemical properties not found in conventional materials. In particular, carbon nanotubes exhibit excellent mechanical properties and electrical characteristics as compared with conventional conductive materials, and studies on the carbon nanotubes have been actively conducted.

Carbon nanotubes are being utilized as components of various composites due to their high electrical conductivity, thermal stability and mechanical strength. However, due to the long length of the carbon nanotubes and the strong attraction between the carbon nanotubes, the polymer has a low dispersion in the polymer material, which shows limitations in terms of applicability and productivity.

One of the methods for solving the problem of dispersion of carbon nanotubes is to improve the dispersibility of carbon nanotubes by impregnating carbon nanotubes with an aqueous acid solution such as nitric acid, sulfuric acid or a mixed solution thereof to oxidize the surface . When the carbon nanotubes are treated with an acid, functional groups of a carboxyl group are formed on the surface of the carbon nanotubes, so that the electrostatic attraction between the carbon nanotubes can be overcome and the dispersibility is improved. However, such an acid treatment has a problem of damaging the surface of the carbon nanotube and deteriorating the physical properties of the carbon nanotube. In addition, the acid treatment process poses another problem as it involves environmental problems such as work stability problems and contamination treatment problems.

Korean Patent Laid-Open Publication No. 10-2010-0113823 discloses dispersible carbon nanotubes, dispersible carbon nanotube-polymer complexes and a method for producing the same.

A conventional method for producing a carbon nanotube composite is characterized in that it comprises at least one organic moiety including a carbon nanotube backbone and a C ₆ -C ₁₄ aromatic functional group having at least one hydroxyl group.

However, the conventional method of producing a carbon nanotube composite has a problem of environmental pollution and waste of energy due to the use of a chemical modifier because it requires chemical modification.

Accordingly, it is an object of the present invention to provide a method for manufacturing a carbon nanotube composite having improved electrical properties by uniformly dispersing carbon nanotubes through a simple preservation method in an existing processing step without using a chemical modifier.

The present invention relates to a method of preparing a suspension of carbon nanotubes by mixing a carbon nanotube and a solvent (step a); Preserving the suspension (step b); Separating the solvent from the suspension to produce wet carbon nanotubes (step c); And mixing the wet carbon nanotube and the polymer melt to produce a carbon nanotube composite (step d).

According to the present invention, the carbon nanotubes are uniformly dispersed in a hydrophilic and hydrophobic fluid through a simple preservation step without adding a chemical modifier, thereby improving the electrical properties of the carbon nanotubes.

1 is a schematic view showing a method for producing a carbon nanotube composite according to the present invention.
FIG. 2 illustrates a method of manufacturing a carbon nanotube composite according to an embodiment of the present invention. Referring to FIG.
FIG. 3 is a method for producing a carbon nanotube composite according to another embodiment of the present invention.
4 is a view illustrating a method of manufacturing a carbon nanotube composite according to another embodiment of the present invention.

The present invention relates to a method of preparing a suspension of carbon nanotubes by mixing a carbon nanotube and a solvent (step a); Preserving the suspension (step b); Separating the solvent from the suspension to produce wet carbon nanotubes (step c); And mixing the wet carbon nanotube and the polymer melt to produce a carbon nanotube composite (step d).

In one embodiment of the present invention, the mixing temperature of the carbon nanotube and the solvent in the step (a) may be 20 to 60 ° C, 25 to 60 ° C or 25 to 50 ° C, .

The carbon nanotube in step a may be 3 to 50 wt%, 3 to 45 wt%, or 5 to 50 wt% based on 100 wt% of the suspension, and the solvent may be selected from alcohols selected from ethanol, methanol, and butanol; An organic solvent selected from hexane, propane, toluene or phenol; Ionic surfactants selected from sodium dodecyl sulfate (SDS) or cetyl trimethyl ammonium bromide (C-TAB); Nonionic surfactants including Tween; Liquid plasticizers; Liquid flame retardants; Polydimethylsiloxane; Aqueous solution of a polymer selected from a polyacrylic acid aqueous solution or a polyalginic acid aqueous solution; And silicone oil.

The suspension storage time in step b may be from 12 hours to 30 days, from 14 hours to 30 days or from 16 hours to 30 days, and the step of preserving the suspension may be a tumbling machine, a stirrer, It may be characterized by using a milling machine.

When the suspension of step c) and the solvent are separated, the temperature may be 20 to 50 ° C, 20 to 45 ° C, 25 to 45 ° C, and the time may be 100 to 200 minutes, 120 to 200 minutes, or 120 to 180 minutes .

The step (d) comprises uniaxially extruding 0.3 to 20 wt%, 0.3 to 15 wt%, or 0.5 to 20 wt% of the wet carbon nanotubes and 80 to 99.7 wt%, 80 to 99.5 wt%, or 85 to 99.7 wt% Biaxial extrusion, compounding mixer or milling machine to produce a carbon nanotube composite.

In another embodiment of the present invention, after the step (b), the suspension may be cooled and thawed. The cooling temperature of the step of cooling and defrosting the suspension may be in the range of minus 5 to minus 30 ° C, minus 10 to minus 30 ° C or minus 10 to minus 25 ° C, and the time may be in the range of 150 to 400 minutes, 180 to 400 minutes, 300 minutes. Also, the thawing temperature of the step of cooling and thawing the suspension may be 20 to 50 ° C, 20 to 45 ° C or 25 to 45 ° C, and the time may be 50 to 150 minutes, 60 to 150 minutes, or 60 to 120 minutes .

In another embodiment of the present invention, the step (b) may include the step of pressing and vacuuming the suspension. The pressure of the step of pressing and vacuuming the suspension may be 5 to 10 bar (gauge pressure), 5 to 9 bar (gauge pressure), or 6 to 9 bar (gauge pressure). Also, the vacuum pressure of the step of pressing and vacuuming the suspension can be from 0 to 3 bar (gauge pressure), from 0 to 2 bar (gauge pressure), or from 1 to 2 bar (gauge pressure).

Accordingly, the present invention provides a carbon nanotube having improved electrical properties by uniformly dispersing carbon nanotubes in a hydrophilic and hydrophobic fluid without adding a chemical modifier.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to illustrate the contents of the present invention, but the scope of the present invention is not limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

FIG. 1 is a schematic view showing a method for producing a carbon nanotube composite according to the present invention.

Referring to FIG. 1, a method for manufacturing a carbon nanotube composite comprises mixing a carbon nanotube (CNT) with a solvent to prepare a suspension in which carbon nanotubes are dispersed. The solvent may be selected from the group consisting of deionized water, ethanol, hexane or polydimethylsiloxane (PDMS), and the content of the carbon nanotubes of the suspension in which the carbon nanotubes are dispersed is 1 to 4% by weight. A twin-screw internal mixer, a stirrer and a vortex mixer may be used as the equipment for producing the suspension.

The suspension prepared in this way is cooled at a temperature of from-5 [deg.] C to -30 [deg.] C for from 150 to 400 minutes. When the suspension is cooled, the cooled suspension is thawed at 20 to 50 DEG C for 50 to 150 minutes.

As the solvent of the suspension is cooled, molecules are inefficiently aligned due to hydrogen bonding between the solvent molecules, and carbon nanotubes are efficiently dispersed.

The cooled and thawed suspension is evaporated at 20 to 50 DEG C for 100 to 200 minutes to separate the solvent.

After the above process, the produced wet carbon nanotube may have a carbon nanotube content of 3 to 80 wt%, and most preferably, 60 to 70 wt%.

The wet carbon nanotubes produced in this manner are mixed with the polymer melt.

The polymer melt may be selected from the group consisting of polydimethylsiloxane, polydimethylsiloxane elastomer, alginic acid suspension and polypropylene, but is not limited thereto.

In particular, when the polymer melt is an alginic acid suspension, the content of alginic acid contained in the alginic acid suspension may be 1 to 3% by weight.

The carbon nanotube composite using the wet carbon nanotube according to the embodiment of the present invention is more excellent in dispersibility than the carbon nanotube composite using no wet carbon nanotube.

< Example  1> Deionized water  Preparation of Wet Carbon Nanotubes as Solvent

Wet carbon nanotubes composed of multi-wall carbon nanotubes (C & T Co. LTD, 10-20 nm diameter, 93% purity) and ionized deionized water were prepared.

First, 3 wt% carbon nanotubes were mixed with 97 wt% deionized water at 25 DEG C and the mixture was stirred at 25 DEG C for 15 minutes with a vortex mixer. After stirring, the suspension was allowed to stand at room temperature for 24 hours for penetration of deionized water molecules into the carbon nanotubes. The suspension was then cooled at -10 DEG C for 240 minutes. The suspension was cooled, and the cooled suspension was allowed to stand at room temperature for 120 minutes and thawed. The thawed suspension was vaporized at 25 DEG C for 150 minutes to separate deionized water as a solvent. Thus, a wet carbon nanotube containing 1.3 wt% of carbon nanotubes was prepared.

< Example  2> Preparation of Wet Carbon Nanotubes Using Ethanol as a Solvent

Wet carbon nanotubes composed of multi-walled carbon nanotubes (C & T Co. LTD, 10-20 nm diameter, 93% purity) and ethanol were prepared.

First, 50 wt% carbon nanotubes were hand-mixed with 50 wt% ethanol at 25 ° C for 10 minutes. After mixing, the mixture was allowed to stand at room temperature for 24 hours for the infiltration of ethanol into the carbon nanotubes. To prevent volatilization of the ethanol, a suspension was prepared by sealing the container. The suspension was then cooled at -10 DEG C for 1 day. The suspension was cooled, and the cooled suspension was allowed to stand at room temperature for 120 minutes and thawed. The thawed suspension was vaporized at 25 DEG C for 150 minutes to separate the solvent, ethanol. A wet carbon nanotube containing 80 wt% of carbon nanotubes was prepared by the above method.

< Example  3> Hexane  Preparation of Wet Carbon Nanotubes as Solvent

Wet carbon nanotubes composed of multi-walled carbon nanotubes (C & T Co. LTD, 10-20 nm diameter, 93% purity) and hexane were prepared.

First, 50 wt% carbon nanotubes were hand-mixed with 50 wt% hexane at 25 DEG C for 10 minutes. After mixing, the mixture was allowed to stand at room temperature for 24 hours for penetration of hexane into carbon nanotubes. To prevent volatilization of the hexane, a suspension was prepared by sealing the container. The suspension was then cooled at -10 DEG C for 240 minutes. The suspension was cooled, and the cooled suspension was allowed to stand at room temperature for 120 minutes and thawed. The thawed suspension was vaporized at 25 DEG C for 150 minutes to separate the solvent, ethanol. A wet carbon nanotube containing 80 wt% of carbon nanotubes was prepared by the above method.

< Example  4> Polydimethylsiloxane  Preparation of Wet Carbon Nanotubes as Solvent

Wet carbon nanotubes composed of multi-walled carbon nanotubes (C & T Co. LTD, 10 to 20 nm diameter, 93% purity) and polydimethylsiloxane (100 cSt to 7 Pas) were prepared.

First, 50 wt% carbon nanotubes were hand-mixed with 50 wt% polydimethylsiloxane at 25 DEG C for 10 minutes. After mixing, the mixture was allowed to stand at room temperature for 24 hours for penetration of polydimethylsiloxane into the carbon nanotubes. To prevent volatilization of the polydimethylsiloxane, a suspension was prepared by sealing the container. The suspension was then cooled at -10 DEG C for 240 minutes. The suspension was cooled, and the cooled suspension was allowed to stand at room temperature for 120 minutes and thawed. The thawed suspension was vaporized at 25 DEG C for 150 minutes to separate the solvent, ethanol. A wet carbon nanotube containing 80 wt% of carbon nanotubes was prepared by the above method.

< Example  5> Preparation of Polydimethylsiloxane-Carbon Nanotube Composites Containing 1.3 wt% Carbon Nanotubes Using Wet Carbon Nanotubes

A polydimethylsiloxane-carbon nanotube composite was prepared using the wet carbon nanotubes prepared in Example 1 above. First, 1.3 wt% wet carbon nanotubes and 98.7 wt% polydimethylsiloxane (viscosity: 7 Pas) were mixed and the mixture was dispersed for 300 minutes using a stirrer. The speed of the disperser was set at 250 RPM. In this manner, a polydimethylsiloxane-carbon nanotube composite containing 1.3 wt% carbon nanotubes was prepared using wet carbon nanotubes. Meanwhile, the polydimethylsiloxane-carbon nanotube composite prepared above was formed by a spin coating method to produce a conductive polydimethylsiloxane film having a thickness of 300 μm.

< Example  6> Preparation of Alginic Acid Suspension-Carbon Nanotube Composite Containing 1.3 wt% Carbon Nanotubes Using Wet Carbon Nanotubes

An alginate suspension-carbon nanotube composite was prepared using the wet carbon nanotubes prepared in Example 1 above. First, an alginic acid suspension was prepared. 2% by weight alginic acid and 98% by weight deionized water were mixed and the mixture was dispersed for 120 minutes using a stirrer to prepare an alginic acid suspension. The alginic acid suspension thus prepared and the wet carbon nanotubes prepared in Example 1 were mixed at 98.7 wt% and 1.3 wt%, respectively. The dispersion was dispersed for 300 minutes using a stirrer and the speed was set at 250 RPM. Thus, an alginate suspension-carbon nanotube composite containing 1.3 wt% carbon nanotubes was prepared using the wet carbon nanotubes. On the other hand, the alginic acid suspension-carbon nanotube composite prepared above was mixed with an aqueous calcium chloride solution to prepare a conductive alginic acid gel having a thickness of 500 mu m.

< Example  Preparation of Polydimethylsiloxane-Carbon Nanotube Composites Containing 1.3 wt% Carbon Nanotubes Using Wet Carbon Nanotubes

A polydimethylsiloxane-carbon nanotube composite was prepared using the wet carbon nanotubes prepared in Example 2 above. First, 1.3 wt% wet carbon nanotubes and 98.7 wt% polydimethylsiloxane (viscosity: 7 Pas) were mixed and the mixture was dispersed for 300 minutes using a stirrer. The speed of the disperser was set at 250 RPM. In this manner, a polydimethylsiloxane-carbon nanotube composite containing 1.3 wt% carbon nanotubes was prepared using wet carbon nanotubes. Meanwhile, the polydimethylsiloxane-carbon nanotube composite prepared above was formed by a spin coating method to produce a conductive polydimethylsiloxane film having a thickness of 300 μm.

< Example  Preparation of Polydimethylsiloxane-Carbon Nanotube Composites Containing 1.3 wt% Carbon Nanotubes Using Wet Carbon Nanotubes

A polydimethylsiloxane-carbon nanotube composite was prepared using the wet carbon nanotubes prepared in Example 3 above. First, 1.3 wt% wet carbon nanotubes and 98.7 wt% polydimethylsiloxane (viscosity: 7 Pas) were mixed and the mixture was dispersed for 300 minutes using a stirrer. The speed of the disperser was set at 250 RPM. In this manner, a polydimethylsiloxane-carbon nanotube composite containing 1.3 wt% carbon nanotubes was prepared using wet carbon nanotubes. Meanwhile, the polydimethylsiloxane-carbon nanotube composite prepared above was formed by a spin coating method to produce a conductive polydimethylsiloxane film having a thickness of 300 μm.

< Example  Preparation of Polydimethylsiloxane-Carbon Nanotube Composites Containing 1.3 wt% Carbon Nanotubes Using Wet Carbon Nanotubes

A polydimethylsiloxane-carbon nanotube composite was prepared using the wet carbon nanotubes prepared in Example 4 above. First, 1.3 wt% wet carbon nanotubes and 98.7 wt% polydimethylsiloxane (viscosity: 7 Pas) were mixed and the mixture was dispersed for 300 minutes using a stirrer. The speed of the disperser was set at 250 RPM. In this manner, a polydimethylsiloxane-carbon nanotube composite containing 1.3 wt% carbon nanotubes was prepared using wet carbon nanotubes. Meanwhile, the polydimethylsiloxane-carbon nanotube composite prepared above was formed by a spin coating method to produce a conductive polydimethylsiloxane film having a thickness of 300 μm.

< Comparative Example  1 > 1.3 wt% Carbon nanotubes containing Polydimethylsiloxane  - Preparation of Carbon Nanotube Composites

1.3 wt% carbon nanotubes and 98.7 wt% polydimethylsiloxane were immediately stirred for 5 hours without the preparation of wet carbon nanotubes. The same as Example 5 except for the use of wet carbon nanotubes.

< Comparative Example  2> 1.3 wt% Alginic acid suspension containing carbon nanotubes - Preparation of carbon nanotube composite

1.3 wt% carbon nanotubes and 98.7 wt% alginic acid suspension were stirred for 5 hours without the production of wet carbon nanotubes. Except for the use of wet carbon nanotubes.

< Experimental Example  1> Evaluation of electrical properties of conductive medium composites

The carbon nanotube composite prepared in Example 5 and Example 6 was repeated five times to measure the surface resistance and the electric conductivity of the molded product by the 4 point probe electrical property measurement method, respectively. In the case of the conductive polydimethylsiloxane film according to Example 5, the electrical conductivity maintained a surface resistance of 10 ⁴ Ohm / sq or less, and in the case of the conductive alginic acid suspension gel according to Example 6, the electrical conductivity was 10 ² Ohm / Electrical conductivity was maintained.

Table 1 shows the surface resistance values of the carbon nanotube composite prepared in Examples 5 and 6 and the surface resistance values of the carbon nanotube composite prepared in Comparative Examples 1 and 2.

Surface resistivity (Ω / sq) when applying wet carbon nanotubes The surface resistivity (Ω / sq) when the wet carbon nanotubes are not used. Conductive polydimethylsiloxane film containing 1.3 wt% carbon nanotubes 10 ⁴ to 10 ⁵ 10 ⁶ to 10 ⁸ Conductive alginic acid gel containing 1.3 wt% carbon nanotubes 10 ² 10 ³ ~ 10 ⁴

The surface resistance values of the carbon nanotube complexes prepared in Examples 7, 8 and 9 and the surface resistance values of the carbon nanotube composite prepared in Comparative Example 1 are shown in Table 2.

menstruum Surface resistance (Ω / sq)
Conductive polydimethylsiloxane film containing 1.3 wt% carbon nanotubes Comparative Example 1 - 8.0x10 ⁵ Example 2 Deionized water 2.0x10 ⁵ Example 7 ethanol 2.4x10 ⁴ Example 8 Hexane 4.5x10 ⁴ Example 9 Polydimethylsiloxane 6.1x10 ⁴

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that such detail is solved by the person skilled in the art without departing from the scope of the invention. will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (13)

Mixing a carbon nanotube and a solvent to prepare a suspension in which the carbon nanotubes are dispersed (step a);
Preserving the suspension (step b);
Separating the solvent from the suspension to produce wet carbon nanotubes (step c); And
(D) mixing the wet carbon nanotube and the polymer melt to produce a carbon nanotube composite,
Further comprising the step of cooling and thawing the suspension between steps b) and c), or a step of pressing and vacuuming the suspension. The method according to claim 1,
The carbon nanotubes of step (a)
Wherein the carbon nanotube composite is immersed in a solvent at 20 to 60 DEG C for 10 hours to 10 days. The method according to claim 1,
Wherein the carbon nanotubes of step (a) are contained in an amount of 3 to 50% by weight based on 100% by weight of the suspension. The method according to claim 1,
Wherein the solvent of step a is selected from the group consisting of alcohols selected from ethanol, methanol or butanol; An organic solvent selected from hexane, propane, toluene or phenol; Ionic surfactants selected from sodium dodecyl sulfate (SDS) or cetyl trimethyl ammonium bromide (C-TAB); Nonionic surfactants including Tween; Liquid plasticizers; Liquid flame retardants; Polydimethylsiloxane; Aqueous solution of a polymer selected from a polyacrylic acid aqueous solution or a polyalginic acid aqueous solution; And silicone oil. &Lt; RTI ID = 0.0 &gt; 21. &lt; / RTI &gt; The method according to claim 1,
Wherein the suspension storage time of the step (b) is from 12 hours to 30 days. The method according to claim 1,
Wherein the step of preserving the suspension of step (b) comprises using a tumbling machine, a stirrer or a milling machine to improve the wetting efficiency of the carbon nanotubes. The method according to claim 1,
Wherein the step (c) comprises separating the solvent in the suspension at 20 to 50 ° C for 20 to 200 minutes to produce a wettable carbon nanotube. The method according to claim 1,
Wherein the solvent separated in the step (c) is reused in the step (a). The method according to claim 1,
The step d) comprises mixing 0.3 to 20% by weight of the wet carbon nanotubes and 80 to 99.7% by weight of the polymer melt by uniaxial extrusion, biaxial extrusion, compounding mixer or milling machine to produce a carbon nanotube composite Tube composite. delete The method according to claim 1,
The step of cooling and thawing the suspension comprises:
Cooling at a temperature of from -5 to -30 캜 for 150 to 400 minutes, and thawing at a temperature of 20 to 50 캜 for 50 to 150 minutes. delete The method according to claim 1,
The step of pressurizing and evacuating the suspension comprises:
Characterized in that it is pressurized at 5 to 10 bar (gauge) at room temperature and vacuumed at 0 to 3 bar (gauge) at room temperature.

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